A comparison of in vitro erosion-like mineral loss between continuous and intermittent acidic exposure with and without human saliva.

AIM: This in vitro study aimed to compare erosion-like mineral loss following intermittent or continuous acidic exposures, and considered the role that human saliva may play. MATERIALS AND METHODS: 180 bovine enamel blocks were divided randomly into four equally-sized groups and exposed to one of the 4 protocols 6 times daily over 6 days (total acidic exposure time of 6h): Group 1, continuous 10 min in orange juice (OJ) followed by 10 min in deionised water; Group 2, continuous 10 min in OJ followed by 10 min in stimulated saliva; Group 3, ten 1-min OJ exposures alternating with ten 1-min deionised water exposures; Group 4, ten 1-min OJ exposures alternating with ten 1-min stimulated saliva exposures. Specimens were stored in a remineralising solution between acidic exposures. Sections were cut and transverse microradiography was used to measure lesion depth in each specimen. RESULTS: Mean (sd) lesion depths were 21.5 (8.1), 21.2 (6.2), 81.7 (12.2) and 72.8 (12.4) μm for Groups 1-4, respectively. Significant differences existed between all protocols except Groups 1 and 2 (mean difference -0.3 μm, 95% CI: -6.1 to 5.5). The mean difference between Groups 3 and 4 was 8.9 μm (95% CI: 3.2-14.7). CONCLUSIONS: Repeated, intermittent exposure to an acidic drink in vitro resulted in greater lesion depth than a continuous exposure of the same duration. Saliva offered some protection against intermittent acidic exposure.